Preview Video

Here's a ComfyUI workflow reality: you spend five minutes generating and processing a video, and your only way to look at the result is to dig through a temp folder or rely on whichever output node happened to render a thumbnail. Preview Video fixes that for anything producing the native VIDEO type. Drop it on the end of a branch, run, and the video plays right inside the node - then you decide whether it's worth saving. It also gives you a download button with a filename you control, and it passes the VIDEO through unchanged so your normal saver can live downstream.

It's the video-output node in ComfyUI ALICE Lab Audio Tools, the brand-new alpha pack (Apache 2.0, no pip deps, bilingual EN/JA) from ALICE Lab. It's a small, honest utility - the kind of node that doesn't do anything fancy and doesn't need to.

How it works

The mechanism is simple: the node takes the VIDEO, saves a temporary MP4 preview through ComfyUI's current video API (video.save_to), and sends that temp file to the frontend for playback. When you hit Save, the browser downloads that temp preview under whatever name you typed - the README is explicit that this is a browser-side download, not the node writing to an arbitrary folder on your server. That distinction matters if you were hoping for a full server-side save node; it isn't one. Use your regular video saver for permanent files and this node for the eyeball check.

Inputs and outputs

• video - the VIDEO to preview (required).
• filename - the download name, default ALICE_Lab_video. It's sanitized (illegal filename characters get replaced, length capped), so you can't accidentally break the download with a weird name.

Single output: video, the same object that went in, unchanged. That pass-through is what lets you chain it before a saver: Preview Video → your Save Video node, and the preview is purely additive.

The traps

The temp previews live in ComfyUI's temp directory and can expire - if a download 404s, it means the temp file was cleaned up; just run the node again to regenerate it. Also keep expectations calibrated: the download is the browser fetching a temp file, so it's not the place to manage a video library. For that, add a proper save node after it. Beyond that, this node is about as close to frictionless as ComfyUI gets.

Install

# ComfyUI Manager → search "ComfyUI ALICE Lab Audio Tools" → Install → restart
# or:
cd ComfyUI/custom_nodes
git clone https://github.com/alice-lab-dev/ComfyUI-ALICE-Lab-Audio-Tools
# restart, then Add Node → ALICE_Lab → Video

Pack-wide requirements: ffmpeg + ffprobe on the ComfyUI process PATH (macOS Homebrew paths auto-checked) and a current ComfyUI with the VIDEO type and comfy_api.latest video APIs. No model downloads, no Python dependencies.